1. FIELD OF THE INVENTION
My invention is in the field of hand tools, and particularly relates to wrenches for gripping usually hexagonal nuts or bolt heads and rotating such nuts or heads. My invention is in a subcategory of this category of wrenches, whereby a bolt or nut can be tightened or loosened by a reciprocating motion of the wrenchhandle about the axis of the bolt or nut--whereby the user avoids problems of access or of limited space for manipulation, without the necessity of the wrench being repetitively removed from and replaced on the nut or bolt head.
2. PRIOR ART
Most wrenches in this subcategory are known as "ratchet wrenches." They make use of a ratchet and pawl, and of separate means for gripping the nut or bolt head. The gripping means may be on a common shaft with the ratchet, or indirectly driven from a shaft on which the ratchet is mounted; or in some cases may be at the center of the ratchet wheel itself, in which case the bolt to be driven, or the bolt on which the nut is being rotated, functions as the common shaft for the ratchet wheel and gripping means. In all of these configurations, however, the gripping means are separate from the ratchet wheel, giving rise to slight increases in bulk, which in occasional circumstances can be a considerable aggravation, and also giving rise to some additional mechanical complexity and cost.
Standard ratchet wrenches of the common-axis type include those familiarly called "socket wrenches"; these are quite expensive and often inconvenient or impossible to use when the clearance above a bolt head is too limited to accommodate the ratchet head and handle, or when a nut is to be rotated on a bolt further from the end of the bolt than the depth of the socket.
Most centerless ratchet wrenches, while designed to avoid or minimize the problems of the "socket" type, yet have these disadvantages:
1. they require some slight clearance above the bolt head for placement and removal of the wrench;
2. they cannot be placed (as can an ordinary end wrench) on a nut which is to be threaded onto a long length of pipe or tubing at a considerable distance from the ends of the pipe or tubing; and
3. they are relatively expensive to manufacture.
Certain special-purpose ratchet wrenches minimize or reduce the first two of these disadvantages, but at the expense of aggravating the third: in these wrenches, both the ratchet wheel and the gripping means are open-ended, and their open ends are capable of being brought into mutual alignment, so that they can be slipped over a pipe, for example, and then moved axially into engagement with a nut. These devices tend to be more elaborate and expensive than ordinary centerless ratchet wrenches. An example of wrenches in this category is the type covered by U.S. Pat. No. 2,954,715, issued Oct. 4, 1960 to C. E. Wycech.
With some very expensive open-end centerless ratchet wrenches it is even possible to move the open end directly onto a nut or bolt head, without any axial motion at all being necessary; these wrenches are generally power-driven, and designed for specialized use by professional craftsmen. Representative of these devices is that disclosed in U.S. Pat. No. 2,711,110, issued June 21, 1955 to A. J. Brame.
None of the devices of which I know provides a true ratchet action in an inexpensive open-ended wrench, such as would be suitable for hand operation by an occasional user.
One commercially available device permits rotating a bolt or nut by generally reciprocating motion of the wrench handle about the axis of the bolt or nut, without need for clearance axially, and at very low cost. This device is an end wrench without moving parts, one jaw of which is cut away to permit back-rotation of the wrench to reengage the bolt head or nut without completely removing the wrench from the head or nut. However, this wrench has the disadvantage that it must be back-swung more than a full one-sixth of a turn (that is, more than 60 degrees) to reengage a hexagonal bolt head or nut, whereas most standard ratchet wrenches reengage every 15 degrees or thereabouts.
Thus I know of no inexpensive open-ended wrench providing the equivalent of ratchet action with a backswing of less than 60 degrees. My invention is directing to supplying such a device.